#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using Graph = vector<vector<int>>;
int main () {
    int N,M; cin >> N >> M;
    string S; cin >> S;
    stack<int> sta;
    stack<int> dic;
    M--;
    if(S[M] == '(') {
        int ans = 0;
        for(int i = 0; i  < N; i++) {
        if('(' == S[i]) {
            sta.push(S[i]);
            dic.push(i);
        }else {
            sta.pop();
            int x= dic.top();
            dic.pop();
            if(x == M) {
                ans = i + 1;
            }
        }
    }
        cout << ans << endl;
    }else {
        int ans = 0;
        for(int i = N - 1; i >= 0; i--) {
            if(')' == S[i]) {
            sta.push(S[i]);
            dic.push(i);
        }else {
            sta.pop();
            int x= dic.top();
            dic.pop();
            if(x == M) {
                ans = i + 1;
            }
        }
        }
        cout << ans << endl;
    }
}